There is no secret sauce in a Bitfi – you don’t need that user’s Bitfi (or any Bitfi, for that matter), the user’s email address, password, access to the Bitfi dashboard or anything else. All you need is the salt and phrase. With those, funds can be accessed.

The Competition

We need to see how others have tried to implement hardware wallets. Most of them don’t work like the Bitfi.

A private key is generated using a random number generator in the wallet.

The private key is displayed on the wallet itself. The user writes it down and stores it safely as a backup.

This is the only time the key is output from the wallet.

From this point onward, the wallet acts as black box, signing any transactions that are sent to it. There is no need to enter the private key, and the private key is never output from the device.

This is probably the most important security feature of a hardware wallet: the private key is locked away in a black box with a limited attack surface and on a device that has a single use. The private key never needs to exist on your malware-infected, general-purpose laptop, and is therefore much less likely to be compromised.

There are still some obvious security issues that need to be handled.

If the wallet is stolen, it could be used to sign transactions. To prevent this, the wallet uses a PIN to guard access to the black box. Without this PIN, the device will not function. Brute-force protection makes it infeasible to try all combinations, preventing the private key from being accessed.

If the wallet is stolen, the private key could be read out from the memory inside the device. To mitigate this, the keys are stored on internal flash on microcontrollers. There is no easy way to read the keys out without advanced hardware attacks.

The wallet simply signs transactions that are sent to it. A user may be expecting to sign “send 2BTC to Bob”. This could be modified to be “send 200BTC to Eve”. To prevent this, the wallet displays the transaction details and asks the user to confirm using buttons on the wallet.

The wallet will run firmware, which can be updated. A malicious firmware could be loaded, allowing the private key to be read, or hide modified transactions from the user. Signed firmware and secure boot are used to protect against this. Only the vendor can generate firmware that the wallet will accept.

These protections are not perfect; a determined and dedicated attacker can still circumvent them. This is a key point: all we need to do is raise the bar high enough that most attackers don’t succeed.

Bitfi

Each and every time you need to sign a transaction, the user enters their entire salt and phrase via the touchscreen display.

The wallet then derives the private key. There is no need for the wallet to store the private key long-term.

Bitfi proudly state that this means there is “nothing to hack” – if there are no keys stored on the device, how can a hacker possibly get the keys?

At first glance, this seems sensible. But if you dig a bit deeper, you quickly realise how broken this concept is. I’m going to describe the attacks we have developed against Bitfi, and how they stack up against competitors.

Cold-boot attack

Description

With USB access to a stolen Bitfi, the salt, phrase and keys can be read from the RAM. This is called a “cold boot attack“.

The data persists in RAM for hours, possibly days.

This only requires a USB cable and a laptop. The wallet casing does not need to be opened, and no specialist hardware is required. No skill is required as the attack is entirely scripted.

The attack takes less than a couple of minutes, and the device works as normal afterwards. It is feasible for this to be carried out during luggage X-ray at an airport, and returned to the user.

There is no requirement to cool the device to perform the attack.

Bitfi recommend the use of “diceware” passwords, which greatly facilitates the recovery of the phrase from memory. The use of a list of dictionary words means there is a lot of redundancy, which in turn means that the memory can degrade significantly and we can still recover the phrase.

Mitigations

To protect yourself, the battery must be removed from the wallet after use. To ensure the keys are no longer in memory, the wallet must be left powered down for at least an hour. During this period, you must make sure no one physically accesses the device.

Competition

The RAM on most other hardware wallets is protected from access via USB or debug protocols such as JTAG or SWD. We have observed no such protections on the Bitfi.

Even with this considered, most other wallets take steps to “zeroise” or wipe the memory immediately after it is used. This limits the window over which cold-boot attacks could be carried out. This is either not performed, or is wholly ineffectual on the Bitfi.

There are no published cold-boot attacks against other hardware wallets.

Malicious Firmware

Description

With USB access to a Bitfi, the firmware can be modified so that the salt, phrase and keys are sent to an attacker the next time they are entered by the user. This permits “evil maid attacks” as well as supply chain tampering.

This only requires USB access to the device. The wallet casing does not need to be opened, and no specialist hardware is required. The attack could be carried out if the Bitfi is connected to a compromised charger or laptop. Using this vector, the attacker never requires physical access to the device.

The attack takes less than a minute, and there are no mechanisms for the user to detect the modification. It is feasible for the attack to be carried out by anyone with access to the device for a short period, either before (supply chain tampering) or after (evil maid) the Bitfi enters possession of a user.

Mitigations

There are no mechanisms for a user to check if the device has been tampered with at a firmware level.

A user could assume that the device is trusted as received from Bitfi. As long as the device does not enter the hands of an attacker, and is never connected to an untrusted USB power source, it could be considered secure from this specific attack.

Assuming the device is trusted as received is therefore high-risk.

Competition

The use of signed firmware updates and secure boot mean that other wallets cannot have their firmware modified in less than a minute using just a USB connection.

There are still other attacks that hardware wallets are vulnerable to.

The wallet can be stolen and replaced in entirety. The replacement will send the PIN to the attacker, allowing them to unlock the stolen wallet and access funds. The user would detect the issue as their key would not be on the replacement wallet, and they would not be able to access funds.

The wallet can be accessed, modified with a hardware implant, and returned. It could harvest the PIN, modify transactions, or spoof integrity checks. This attack is significantly more challenging that simply plugging the device into USB, and to-date, no feasible attack has been shown against any of the popular wallets.

Shoulder surfing

Description

The entire salt and phrase need to be entered into the Bitfi each time it is used. This is entered using a conventional touchscreen, with a QWERTY keyboard, and displayed on the screen clearly.

It is entirely possible to read the salt and phrase from the screen and then use this to steal funds from the user.

Even without direct view of the screen, the finger position when typing allows characters to be inferred. The use of dictionary words means that even if certain characters cannot be determined, they can be inferred from those that can be seen.

As the salt and phrase contain all the information required to steal funds, a user may be entirely unaware that they have been compromised. The attacker can delay the attack until an opportune moment.

Mitigations

The Bitfi wallet cannot be used when someone can observe the device.

Competition

Whilst the PIN can be shoulder-surfed on other devices, an attacker still requires access to the wallet itself to obtain the key. This provides a significant additional layer of security.

Some other wallets mitigate the risk of shoulder surfing by randomising PIN layout.

Key entropy

Description

The Bitfi device allows users to choose their own salt and pass phrase. Multiple studies have shown users are very bad at choosing and storing passwords, and there is no reason to assume that Bitfi will differ.

Mitigations

Competition

Competing wallets encourage the use of keys that are randomly generated using a good source of entropy, removing the human aspect.

Something-you-have and something-you-know

Description

Bitfi only requires the salt and phrase, and nothing else. Wallets can be used interchangeably (at least, at a functional level – this is not recommended for security reasons).

If your salt and phrase leak via any means, an attacker has access to your funds. There are no flags to signal this.

This is termed single-factor authentication.

Mitigations

There are no good means to solve this issue.

Competition

Other wallets support passphrases as part of the BIP39 specification. To use the wallet, you need both the key stored in the wallet itself, and a passphrase that is stored elsewhere. This is something-you-have (the key on the wallet) and something-you-know (the phrase).

Use of a passphrase with BIP39 significantly elevates the security above that of a Bitfi.

Conclusion

The Bitfi wallet is less well protected than competing hardware wallets. If you ever let anyone else have access to it, ever connect it to an untrusted device, or use it in a public place, you are not safe.

Users of Bitfi must take significant and limiting steps to mitigate the risk they are exposed to.

Even ignoring Bitfi’s dishonest behaviour, the product has little to recommend it over any other wallet.

Can these issues be fixed?

We aren’t really sure.

There is no hardware root of trust on the Bitfi. This must be burned into the device before it leaves the vendor’s possession for it to be secure. Without this, secure boot cannot be implemented well.

The use of external RAM on a commodity chipset (without RAM encryption) will always leave the keys exposed, no matter how well you try to wipe them from software.

Android is a poor choice of operating system. It makes wiping memory very challenging – the salt and phrase are in tens of locations. It also makes limiting the attack surface very, very hard.

Earlier this week, cryptocurrency news was full of stories about a new hardware wallet: the Bitfi.

What makes this one any different?

John McAfee claims it is “unhackable”. Not just “harder to hack”, but “unhackable”.

That’s a bold claim. They know it’s a bold claim, so they have set a bounty.

Sounds great, no?

No.

The bounty deliberately only includes only one attack: key recovery from a genuine, unaltered device. And the device doesn’t store the key.

The only way to win the bounty is to recover a key from a device which doesn’t store a key.

There are many, many more attacks such a device is vulnerable to. The most obvious one: modifying the device so that it records and sends the key to a malicious third party. But this is excluded from the bounty.

Why is this?

Because the bounty is a sham. When it lays unclaimed, Bitfi can say “our device is unhackable”. What it actually means is “our device is not vulnerable to one specific attack”.

I’m going to put a challenge to them.

If their device is unhackable, then change your bounty terms:

A trusted intermediary is chosen e.g. a lawyer or judge.

We provide the trusted intermediary with three Bitfi devices, a laptop computer and a WiFi access point.

The trusted intermediary puts $1,000,000 directly onto each Bitfi device, using the laptop and WiFi access point we have provided.

They must follow the publicly available documentation, without interference from anyone.

These are much stronger security goals to meet, and much more accurately emulate the real world.

If Bitfi won’t change the terms, it’s clear to me that they don’t stand behind their claims that the device is unhackable.

On 25th August, I received the above email purporting to be from ParentPay. ParentPay is an online payment system designed for use by schools – you can book and pay for school dinners, library fines, school trips etc.

I am a user of the application, but I’ve only casually (and observationally) looked at the security of their main web application. I have no complaints, although the SSL configuration is less than optimal.

This email looks like a textbook phishing email. I had to spend some time confirming it was genuine, and was only really convinced after they tweeted about the same competition.

Why does it look like a phishing email?

The sender’s email address is not on the domain parentpay.com – it is parentpay@emarketing.education.co.uk. This teaches your users to accept that any email containing the word parentpay is genuine.

You are tempting users with vouchers in return for logging in. This is a standard technique used by phishers.

Amazon is not capitalised. Spelling and grammar mistakes are common in phishing emails.

The login link labelled “Login to ParentPay” takes us to the ParentPay login page. In a phishing email, it would take us to a malicious site that may harvest our details or deliver malware. Conditioning users to login via links sent in email is a bad idea.

The login link directs us to the education.co.uk domain, which redirects to ParentPay. Teaching users to follow links to third-party sites to login is a monumentally bad idea – a number of attacks can be carried out like this including a plain phishing page, tabnabbing etc.

Please don’t send emails like this – it doesn’t just impact the security of your site. Conditioning users to trust emails like this goes against a lot of user awareness training, regardless of which site they are accessing.

NeighbourNET (caution, awful Flash splash page) is a platform used to power a number of local community websites in London:

www.ActonW3.com

www.BrentfordTW8.com

www.ChiswickW4.com

www.EalingToday.co.uk

www.FulhamSW6.com

www.HammersmithToday.co.uk

www.PutneySW15.com

www.ShepherdsbushW12.com

www.WandsworthSW18.com

www.WimbledonSW19.com

It would be fair to say the visual presentation of the sites hints at there being security problems.

1. No passwords required for login

When you login to the site, all you need is an email address. There are no passwords at all.

2. Posting name can be spoofed

The posting name and email is passed as a parameter when posting a message, and it can be altered to any value you want.

This allows you to post as anyone else on the forum.

3. No cross-site request forgery protection

No requests to the site have any cross-site request forgery protection.

A user can visit another website, and that website can cause them to carry out actions on the site, such as posting messages.

4. Allows embedding of untrusted third-party content

The site embeds it’s own content using a URL passed as a GET parameter.

The source of this content is not whitelisted or validated, so you can just embed your own content. This has only been tested with plain HTML, but if JavaScript, Flash or other content could be embedded, this would lead to cross-site scripting or malware delivery to users.

Conclusion

A mess of security issues. Considering that local councillors use these sites to communicate with the public, allowing impersonation is a serious issue.

Disclosure timeline:

The operators of the sites were informed on 4th May, so after 60 days they are being disclosed.

14/06/2016 – chase on further response and state disclosure date of around 04/07/2016. Email acknowledged.

17/06/2016 – get response from vendor:

Chatted to the development team about the issues you raised.

They acknowledged that you have identified some potential security holes but they have existed for a long time without ever been exploited and there seems little incentive for anyone to try to do so.

We have been for some time now working on completely overhauled site architecture and whilst this project has been ongoing for sometime we are now talking in terms of months rather than years before implementation. This would close these security holes and others.

The release of the CSL Dualcom report last week has caused quite a stir in the security industry. With just shy of 60,000 page views, thousands of tweets, many forum discussions, and one particularly lively thread on Reddit, many people in both the security and IT industries have read the work. Two clear comments have been made many times:

Yes, this crypto is really bad.

How did CSL Dualcom mess up handling this so badly?

If you want to fix the crypto, there are many places you can go.

If you want to handle vulnerabilities better though, I hope I can give you some advice. I’ve now dealt directly with CSL, Risco, Visonic, Dedicated Micros, Samsung, Motorola, Texecom and WebWayOne and think that I have learnt a lot about the disclosure process.

Make reporting issues easy

The first step of reporting a vulnerability is contacting someone. At worst, this requires multiple emails, tweets, phone calls, and LinkedIn prodding. Some companies have taken several months to respond, and when they do, they ask questions to check that you are eligible to receive support. Others have responded and dealt with issues in under 24 hours.

Make this easy. Have a page on your site, ideally with an email address security@panelmaker.com. Have an auto-responder on this email address, informing the reporter what the next steps are. Get back to them quickly.

Have a vulnerability disclosure policy

None of the vendors had a vulnerability disclosure policy. This means the reporter has no idea how their work will be handled – are they going to be welcomed with open arms? Threatened with legal action? Can they disclose the vulnerability?

You should have a simple and fair vulnerability disclosure policy. We realise you are dealing with potentially legacy products that are hard to update, so give yourselves a long period of time to deal with issues.

Allow researchers to disclose the issues once fixed or mitigated. This gives both parties benefits – you get free security testing done, the reporter gets reputation, and customers can see how responsive you are.

Pass it by your solicitor to make sure you are not digging your own grave.

Do not require a non-disclosure agreement

As an independent security consultant, it is essential that I do not go around signing NDAs willy-nilly.

They provide me with no benefit. There is virtually nothing that a vendor can disclose about me, but I have a lot I can disclose about them.

At the same time, they put me at risk. The vendor has little legal risk – what can I sue them for, if they have nothing to disclose? Equally, they can sue me as I hold a lot of secrets.

NDAs prevent me discussing work with existing customers. If I sign an NDA with CSL, I then can’t advise my other customers in detail about CSL’s mistakes.

Do not be threatening

Do not make any implied or actual threats, especially legal ones.

You can be in absolutely no doubt that if one person can find the issues, so can another. And that other person may not be so amenable.

Work with the researcher

In more than a few cases, the vendor made fixes for an issue, but the fixes also had problems. In some cases, they even make problems worse.

A prime example of this is reporting a backdoor password, and the vendor simply changes the backdoor password…

Check with the researcher if the fix actually solves the problem, or you will just end up with multiple vulnerabilities being disclosed.

Realise that you are Internet connected

15 years ago, signalling devices were neatly partitioned from the Internet. They had dedicated communications channels and infrastructure.

As devices added IP, they were treated as signalling devices that happen to have an IP side. They were still treated as alarm products, and not Internet connected devices. The threat model had stuck at “Billy Burglar”.

Nowadays, this attitude is still common. But devices have changed – most of them connect to or via the Internet. You need to include “Hacker” into your threat modelling. Fundamentally, a lot of attacker don’t even care if you device is an alarm – they just want another box that is able to generate traffic or send spam as part of a botnet.

You need to involve people who are versed in information security.

Avoid ending up with disclosure handled by CERT/CC

Don’t get me wrong – I love CERT/CC and what they do, but it is disasterous for a company to end up with a vulnerability on their product there. It sends a very strong signal out to the IT community that the company has had ample chance to respond to an issue and they haven’t. It also gives massive exposure to issues – over 1000 tweets showed up within 6 hours of the CSL issue being disclosed.

RSI Videofied are a French company that produce a series of alarm panels that are fairly unique in the market. They are designed to be battery powered and send videos from the detectors if the alarm is triggered. This is called video verification. They are frequently used on building sites and disused buildings.

They send data over either GPRS (mobile) or IP. Whilst reverse engineering as part of competitor analysis for a client, I found a large number of vulnerabilities in the protocol they use to communicate.

In summary, the protocol is so broken that it provides no security, allowing an attacker to easily spoof or intercept alarms.

As appears to be the norm in the physical security world, the vendor failed to respond over the course of 6 weeks, so this was taken to CERT/CC for disclosure. They are due for disclosure 30 November 2015. CERT/CC have released their report.

This looks like some kind of challenge/response. EA00121513080139 is the panel’s serial number. 1440 is the account number for that particular panel.

Brief entropy analysis of the long strings in AUTH1, AUTH2, and AUTH3 showed them to be random.

A Python script was created to mimic the panel.

It was noted that if the serial number was altered, the response was different:

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R:IDENT,1000

S:IDENT,EA00121513080136,2

R:SETKEY,10680211105310035016110010318802

R:VERSION,2,0AUTH1,D5689F494D81ECA07E72CC0F3459ED4E

It appears that the first time a particular server sees a serial number, it informs the panel of the key used for the challenge/response. If we then attempt to connect again, the key is not shown to us.

It was then seen that connecting the panel to a new server at a different alarm receiving centre delivered exactly the same key. This means that the key is deterministic. It also means that to obtain the key for any given panel, all we need to do is send the serial number to another Videofied server (of which there are many).

However, we can go further than this. Notice that the key delivered above has a lot of common numbers with the serial number. It appears that the key is just a mixed up serial number:

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R:IDENT,1000

S:IDENT,0000000000000000,2

R:SETKEY,00000000000010000000000000010000VERSION,2,0A

R:AUTH1,6587DA1323597F4AC986936BAF20102B

R:IDENT,1000

S:IDENT,0000000000000020,2

R:SETKEY,00000000000210000000000000210000

R:VERSION,2,0AUTH1,0A79588F06FEB594D153237230BA0D61

R:IDENT,1000

S:IDENT,0123456789ABCDEF,2

R:SETKEY,40FB05D68C7E10A97A4FD6C080E1BB05

R:VERSION,2,0AUTH1,D4F98DF37EF53F52505599D833484658

This means that we can trivially determine the key used for authentication using the serial number that is sent in the plain immediately beforehand.

The challenge response protocol is as follows:

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Server:Random server challenge

Panel:AES(Random server challenge,key)|Random panel challenge

Server:AES(Random panel challenge,key)

Now that we have the key, it is very easy for us to spoof this.

Python

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importsocket

fromCrypto.Cipher importAES

fromCrypto importRandom

# 4i Security's server and port

rsi_server='rsi.videofied.com'

rsi_port=888

# This is the valid alarm serial

serial='A3AAA3AAA2AAAAAA'

s=socket.socket(socket.AF_INET,socket.SOCK_STREAM)

s.connect((rsi_server,rsi_port))

# Open a connection to the server should see

# IDENT,1000

print'R:',s.recv(1024)

# This is the valid serial number from the board

msg='IDENT,'+serial+',2\x1a'

print'S:',msg

s.send(msg)

# Should receive

# VERSION,2,0

print'R:',s.recv(1024)

# AUTH1,<16 byte challege>

auth1=s.recv(1024)

print'R:',auth1

# Split out challenge

challenge=auth1.split(',')[-1][:-1]

print'Challenge:',challenge

# The key is just a jumbled up serial.

# This means the key is entirely deterministic and can be guessed from one sniffed packet.

Authentication decoupled from identity

The above authentication ensures that a given panel with a serial number knows the key. Even if this key was secret and non-deterministic, it is entirely decoupled from the identity of the account. The account is the piece of information identifying the panel to the alarm receiving centre.

Notice that in the above authentication, the account number 1440 is not encrypted or linked to the panel serial:

It turns out that we can simply re-program the panel to use site 1441, and it will report into the alarm receiving centre as account 1441. There is no tie to the serial number, and no authentication of the account number.

Other basic crypto failings

Beyond the authentication being totally broken, the protocol suffers from further basic issues:

Nothing is encrypted – anyone can view the content of the messages, including the videos.

There is no integrity protection such as a message authentication code or even a checksum, meaning that it is easy for messages to be altered deliberately or by accident.

There are no sequence numbers, which means that messages can be replayed and there is no end-to-end acknowledgement of alarm reception

Conclusion

The RSI Videofied system has a level of security that is worthless. It looks like they tried something and used a common algorithm – AES – but messed it up so badly that they may as well have stuck with plaintext.

CWE-327: Use of a Broken or Risky Cryptographic Algorithm – CVE-2015-7286

CWE-255: Credentials Management – CVE-2015-7287

CWE-912: Hidden Functionality – CVE-2015-7288

The purpose of this blog post is to act as an intermediate step between the CERT disclosure and my detailed report. This is for people that are interested in some of the detail but don’t want to read a 27-page document.

First, some context.

What are these CSL Dualcom CS2300-R devices? Very simply, they are a small box that sits between an intruder alarm and a monitoring centre, providing a communications link. When an alarm goes off, they send a signal to the monitoring centre for action to be taken. They can send this over a mobile network, normal phone lines, or the Internet.

They protect homes, shops, offices, banks, jewellers, data centres and more. If they don’t work, alarms may not reach the monitoring centre. If their security is poor, thousands of spoofed alarms could be generated. To me, it is clear that the security of these devices must be to a reasonable standard.

I am firmly of the opinion that the security of the CS2300-R devices is very poor. I would not recommend that new CSL Dualcom signalling devices are installed (regardless of model), and I would advise seeking an alternative provider if any were found on a pen-test. This is irrespective of risk profile of the home or business.

If you do use any Dualcom signalling devices, I would be asking CSL to provide evidence that their newer units are secure. This would be a pen-test carried out by an independent third-party, not a test house or CSL.

What are the issues?

The report is long and has a number of issues that are only peripheral to the real problems.

I will be clear and honest at this point – the devices I have tested are labelled CS2300-R. It is not clear to myself or others if these are the same as CS2300 Gradeshift or any other CS2300 units CSL have sold. It is also not clear which firmware versions are available, or what differences between them are.

The devices were tested in the first half of 2014.

CSL have not specifically commented on any of the vulnerabilities. On the 20 November they finally made a statement to CERT.

Here is a summary of what I think is wrong.

1. The encryption is fundamentally flawed and badly implemented

The encryption cipher used by the CSL devices is one step above the simple Caesar Cipher. The Caesar Cipher is known and used by many children to encrypt messages – each character is shifted up or down by a known amount – the “key”. For example, with the key of “4”, we have:

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Plain text:THE QUICK BROWN FOX JUMPED OVER THE LAZY DOG

Key:444444444444444444444444444444444444

Cipher text:XLI UYMGO FVSAR JSB NYQTIH SZIV XLI PEDC HSK

CSL’s encryption scheme goes one step further, and uses a different shift as you move along the message. It’s a hybrid between a shift cipher and a polyalphabetic substitution cipher.

The mechanism the algorithm uses is like so:

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Plain text:THE QUICK BROWN FOX JUMPED OVER THE LAZY DOG

Key:439837469748612821721892179149127197

Cipher text:XKN YXPGQ KYSET GQF LVTRFL XXFY CII UBBF EXN

The first character is shifted up by 4, the next by 3, then 9, 8, 3 etc. This is simplified, but not by much.

It would be fair to say that this encryption scheme is very similar to a Vigenère cipher, first documented in 1553, even used fairly widely until the early 1900s. However, today, even under perfect use conditions, the Vigenère cipher is considered completely broken. It is only used for teaching cryptanalysis and by children for passing round notes. It is wholly unsuitable to use for electronic communications across an insecure network.

Notice that I said the Vigenère cipher was broken “even under perfect use conditions”. CSL have made some bad choices around the implementation of their algorithm. The cipher has been abused and is no longer in perfect use conditions.

An encryption scheme where the attacker knows the key and the cipher is totally broken – it provides no protection.

And CSL have given away the keys to the kingdom.

The key is the same for every single board. The key cannot be changed. The key is easy to find in the firmware.

An encryption scheme where the attacker knows the key and the cipher is completely and utterly broken.

Beyond that, CSL make a number of elementary mistakes in the protocol design. Even if the key is not known and fixed, it could easily be recovered from observing a very limited number of sent messages. The report details some of these mistakes. They aren’t subtle mistakes- they are glaring errors and omissions.

I cannot stress how bad this encryption is. Whoever developed it doesn’t even have basic knowledge of protocol design, never mind secure protocol design. I would expect this level of work to come from a short coursework from A-level IT students, not a security company.

2. Weak protection from substitution

The CS2300-R boards use two pieces of information to identify themselves. One is the 20-digit ICCID – most people would know this as the number on a SIM card. The other is a 6-digit “chip number”.

Both of these are sent in each message – the same message which we can easily decrypt. This leads to an attacker being able to easily determine the identification information, which could then be used to spoof messages from the device.

Beyond that, installers actually tweet images of the boards with either the ICCID or chip number clearly visible: 1, 2, 3.

This is a very weak form of substitution protection. There are many techniques which can be used to confirm that an embedded device is genuine without using information sent in the open, such as using a message authentication code or digital signature.

3. Unable to perform firmware updates over-the-air

It is both presumptuous and foolhardy to assume that the device you deploy on day one will be free of bugs and security issues.

This is why computers, phones, routers, thermostats, set-top boxes, and even cars, allow for firmware updates over-the-air. Deployed devices can be updated in the field, after bugs and vulnerabilities have been fixed.

It has been considered – for many years – that over-the-air firmware updates are an absolutely vital part of the security of any connected embedded system.

The CS2300-R boards examined have no capability for firmware update without visiting the board with a laptop and programmer. No installers that I questioned own a programmer. The alarm system needs to be put into engineering mode. The board needs to be removed from the alarm enclosure (and, most of the time it is held in with self-adhesive pads, making this awkward). The plastic cover needs to be removed. The programmer needs to be connected, and then the firmware updated. Imagine doing that for 100 boards, all at different sites.

At this point, we need to remember that CSL claim to have over 300,000 deployed boards.

If we imagine that it takes a low estimate of 5 minutes to update each of the 300,000 boards, that is over 1000 man-days of effort to deploy an update. If you use a more realistic time estimate, the amount of effort becomes scary.

This means that any issues found cannot and will not be fixed on deployed boards.

CSL have confirmed that none of their devices support over-the-air firmware updates.

CSL have given away the keys to the kingdom and cannot change the locks.

A software development life-cycle that has a product that cannot be updated fosters a do-not-care attitude. Why should CSL care about vulnerabilities if they cannot fix them? What would be their strategy if there was a serious, remotely exploitable vulnerability was found?

4. I do not believe the CS2300-R boards are standards compliant

One of the standards governing alarm signalling equipment is EN50136. These are a series of lengthy documents that are unfortunately not open access.

Only a small part actually discusses encryption and integrity. Even when they are discussed, it is in loose terms.

CSL have stated, in reference to my report:

As with all our products, this product has been certified as compliant to the required European standard EN-50136

Unfortunately, CSL will not clarify which version of the standards the CS2300-R devices have been tested to.

When symmetric encryption algorithms are used, key length shall be no less than 128 bits. When other algorithms are deployed, they shall provide similar level of cryptographical strength. Any hash functions used shall give a minimum of 256 bits output. Regular automatic key changes shall be used with machine generated randomized keys.

Hash functions and encryption algorithms used shall be publicly available and shall have passed peer review as suitable for this application.

These security measures apply to all data and management functions of the alarm transmission system including remote configuration, software/firmware changes of all alarm transmission equipment.

There are newer versions of the standard, but they are fundamentally the same.

My interpretation of this is as follows:

Cryptography algorithms used should be in the public domain and peer reviewed as suitable for this application.

We are talking DES, AES, RSA, SHA, MD5. Not an algorithm designed in-house by someone with little to no cryptographic knowledge. The cryptography used in the CS2300-R boards examined is unsuitable for use in any system, never mind this specific application.

When the algorithm was sent as a Python script to one cryptographer, they assumed I had sent the wrong file because it was so bad.

The next I sent it to said:

I’ve never thought I’d see the day that someone wrote a variant on XOR encryption that offered less than 8 bits of security, but here we are.

We’re talking nanosecond scale brute force.

Key length should be 128 bits if a symmetric algorithm is used.

A reasonable interpretation of this requirement is that the encryption should provide strength equivalent to AES-128 from brute-force attacks. AES-128 will currently resist brute-force for longer than the universe has existed. This is strong enough.

The CSL algorithm is many orders of magnitude less secure than this. Given the fixed mapping table, a message can be decrypted in the order of nanoseconds.

Regular is obviously open to interpretation. There is a balance to be struck here. You need to change keys often enough that they cannot be brute-forced or uncovered. But key exchange is a risky process – keys can be sniffed and exchanges can fail (resulting in loss of communications).

Regardless, the CS2300-R boards have no facility at all for changing the keys. The key is in the firmware and can never change.

All data and management functions including remote configuration should be protected by the encryption detailed.

The CS2300-R have a documented SMS remote control system, protected by a 6-digit PIN. This is not symmetric encryption, this is not 128-bit, this is not peer-reviewed.

This is a remote control system protected by a short PIN (and it seems that PIN is often the same – 001984 – and installers don’t have the ability to change it).

Data should be protected from accidental or deliberate alteration

The message can easily be altered by accident or by malice. Look at this example:

1

2

3

4

5

Status:89441012345678901237A1234561111111111111117

Encrypted:2i7MZCNhHRdkZpYTX2fiLMIaEbo02SKe5L3EbPYWRkn

Shift:0000000000000000000000000004444444444444440

Altered:2i7MZCNhHRdkZpYTX2fiLMIaEbo46WOi9P7IfT20Von

Decrypted:89441012345678901237A1234565555555555555557

By adding four to a character in the encrypted text, we add four to the decrypted character. This means that the message content has been altered significantly, and very easily. The altered part of the message is the alarm status.

I can see no way that these units are compliant with this standard. CSL, however, say they are certified.

5. I do not believe third-party certification is worthwhile

It’s still not actually clear which units have been tested. The certificate says CS2300, my units say CS2300-R, but CSL say that the units I have looked at have been tested.

After meeting with the test house I have an idea of what happened here.

The test house would not discuss the CS2300 certification specifically, due to client confidentiality. They did discuss the EN50136 standard and testing in general.

Firstly, I was not reassured that the test house has the technical ability to test any cryptographic or electronic security aspects of the standard. Their skills do not lie in this area. At a number of points during the meeting I was surprised about their lack of knowledge around cryptography.

Secondly, there are areas of standards where a manufacturer can self-declare that they are compliant. The test house expected, if another unit was to be tested, the sections on encryption and electronic security would be self-declared by the manufacturer. Note that the test house can still scrutinise evidence around a self-declaration.

Thirdly, there is no way for a third-party to see any detail around the testing without both the manufacturer and test house agreeing to release the data. To everyone else, it’s just a certificate.

From this, I can infer that the CS2300 – and probably other signalling devices, even from other manufacturers – have not actually had the encryption or other electronic security tested by a competent third-party.

I don’t feel that this is made clear enough by either manufacturers or test houses.

6. I do not think the standard is strict enough

I acknowledge that the standard must cover a range of devices, of different costs, protecting different risks, and across the EU. It must be a lot of work drawing up such a standard.

Regardless of this, the section on encryption and substitution protection is so wishy-washy that it would be entirely possible to build a compliant device that had gaping security holes in it.

Encryption, by itself, is not enough to maintain the security of a system. This is widely known in the information security and cryptography world. It’s perfectly possible to chain together sound cryptographic primitives into a useless system. There is nothing in the standard to protect against this.

7. CSL do not have a security culture

There are so many issues with the CS2300-R system it is almost unbelievable.

(It is worth noting that CSL added TLS to their shop and fixed the VPN server after I blogged about them a few weeks ago – why does it take blog posts before trivially simple issues are fixed?)

CSL do not have a vulnerability disclosure policy. It was clear that CSL did not know how to handle a vulnerability report.

CSL have refused to discuss any detail without a non-disclosure agreement in place.

There is no evidence that CSL’s security has undergone any form of scrutiny. Even a rudimentary half-day assessment would have picked up many of the issues with their website.

There is also a degree of spin in their marketing and sales. A number of installers and ARCs questioned believe that the device forms a VPN to CSL’s server. Some also believe that the device uses AES-256. Indeed, their director of IT, Santosh Chandorkar claimed to me that the CS2300-R formed a VPN with their servers. There is no evidence in the firmware to support any of these claims, but there is also no way for a normal user to confirm what is and isn’t happening.

At a meeting, Rob Evans inferred that it would be my fault should these issues be exploited after I released them. He used the example of someone getting hurt on a premises protected by their devices. It obviously would not the fault of the company that developed the system.

IP requires elaborate encryption because it sends data across the open Internet. In my 25 years’ experience I’ve never been aware of a signalling substitution or ‘hack’, and have never seen the need for advanced 128 bit encryption when it comes to traditional security signalling.

No need for 128 bit encryption, Simon. Only the standard.

Conclusion

The seven issues to take away from this are:

CSL have developed incredibly bad encryption, on a par with techniques state-of-the-art in the time before computers.

CSL have not protected against substitution very well

CSL can’t fix issues when they are found because they can’t update the firmware

There seems to be a big gap between the observed behaviour of the CS2300-R boards and the standards

It’s likely that the test house didn’t actually test the encryption or electronic security

Even if a device adheres to the standard, it could still be full of holes

CSL either lack the skill or drive to develop secure systems, making mistake after mistake

What do I think should happen as a result of this?

All signalling devices should be pen-tested by a competent third-party

A cut-down report should be available to users of the devices, detailing what was tested and the results of the testing

The standards, and the standards testing, needs to include pen-testing rather than compliance testing

The physical security market needs to catch up with the last 10 years of information security

Rebuttals

CSL have made some statements about this.

This only impacts a limited number of units

CSL have stated:

Of the product type mentioned in his report there are only around 600 units in the field

If it is only a subset of units labelled CS2300-R, how does a user work out which ones are impacted?

The other 299,400 devices may not be the same unit, but how do they differ? Has a competent third-party tested the encryption and electronic security?

We have done an internal review

CSL have stated:

Our internal review of the report concluded there is no threat to these systems

Ask yourself this: if someone has deployed a system with this many issues in it, why should you trust their judgement as to the security of the system now? Are they competent to judge? There is no evidence that they are.

They have been third-party tested

CSL have stated, specifically in reference to my report:

As with all our products, this product has been certified as compliant to the required European standard EN-50136

This worries me. This says that the very device I have examined – the one full of security problems – got past EN-50136 testing. If this device can pass, practically anything can pass.

But I am fairly sure that the standards testing essentially allows the manufacturer to complete the exercise on paper alone.

The devices are old

The product tested was a 6 year old GPRS/IP Dualpath signalling
unit.

Firstly, there are at least 600 of these still in service.

Secondly, when the research was carried out, the boards were 4.5 years old.

Thirdly, does that mean that a 6 year old product is obsolete? Does that mean they don’t support it any more?

The threat model isn’t the one we are designed for

This testing was conducted in a lab environment that isn’t
representative of the threat model the product is designed to be implemented in
line with. The Dualpath signalling unit is designed to be used as part of a
physically secured environment with threat actors that would not be targeting
the device but the assets of the device End User.

This seems to have been a sticking point with some of the more backwards members of the security industry as well.

The reverse engineering work was done in a lab. As with nearly all vulnerability research, there needs to be a large initial investment in time and effort. Once vulnerabilities have been found, they can be exploited outside of the lab environment.

If the threat actors aren’t targeting the device, why bother with dual path?

Again, it doesn’t look like the devices comply with the standards. This is what counts.

They aren’t remotely exploitable

No vulnerabilities were identified that could be exploited remotely via
either the PSTN connectivity or GPRS connection which significantly reduces the
impact of the vulnerabilities identified.

I disagree with this. CSL and a number of their supporters do not seem to want to accept that GPRS data can no longer be classed as secure.

This still leaves the gaping holes on the IP side. When I met CSL at IFSEC 2014, they strongly implied that the number of IP units they sold was negligible. There seem to be more than a few getting installed though.

The price point is too low

The price point for the DualCom unit is £200 / $350. CSL DualCom also
have devices in their portfolio that are tamper resistant or tamper evident to
enable customers to defend against more advanced or better funded threat
actors. Customers are then able to spend on defence in line with the value of
their assets.

I’m not sure why the price is relevant. Are CSL saying it’s too cheap to be properly secure?

I can’t find any of these tamper resistant or tamper evident devices for sale – it would be interesting to see what they are.

Very few of the issues raised involve physically tampering with the device. They are generally installed in a protected area.

These aren’t problems, but we are releasing a product that fixes the issues

If customers are concerned about the impact of these vulnerabilities CSL are
releasing a new product in May which addresses all of the areas highlighted.

So on one hand, these vulnerabilities aren’t issues, but they are issues enough that you’ve developed a new product to fix them? Righty ho.

Firmware updates are vulnerable, but not normal communications

CSL products are not remotely patchable as we believe over the air updates
could be susceptible to compromise by the very threat actors we are defending
against.

What?

Just a few paragraphs ago, you say that you are not protecting against the kind of threat actor that can carry out attacks as in the report. But you are protecting against a threat actor that can intercept firmware updates?

Why allow critical settings to be changed over SMS if this is an issue?

What-if rebuttals

These are things that haven’t been directly stated by CSL or others, but I suspect that people will raise them

These issues are not being exploited

During discussions with CSL, they seemed very focused on what has happened in the past. I had no evidence of attacks being carried out against their system, and neither did they. Therefore, in their eyes, the vulnerabilities were not an issue.

We don’t mind issues being brought to us privately

He works for a competitor

Firstly, I don’t. I have spoken to competitors to find out how they work.

Secondly, this would not detract from the glaring holes in the system.

He is blackmailing people in the security industry

I have released vulnerabilities in Visonic and Risco products. Shortly, there will be a vulnerability in the RSI Videofied systems. None of these people have been asked for payment and have been given 45+ days to respond to issues. This is a fair way of disclosing issues.

I do paid work with others in the security industry. Again, at no point has payment been requested to keep issues quiet.

I have never asked CSL for payment. At several points they have asked to work with me, which I have turned down as I don’t think their security problems are going to be resolved given their culture.

The encryption and electronic security are adequate

It’s hard to explain (to someone outside of infosec) just how bad the encryption is. It is orders of magnitude less strong than encryption used by Netscape Navigator in 2001.

The problems found have been widely known for 20+ years, and many are easy to protect against. Importantly, it appears that their competitors – at least WebWayOne and BT Redcare – aren’t making the same mistakes.

The GPRS network is secure

This was true 15 years ago. It is now possible – cheaply and easily – to spoof a cell site and then intercept GPRS communications. You cannot rely on the security of the GRPS network alone.

Further to this, exactly the same protocol is used over the Internet.

But above all, the standards don’t differentiate between GPRS and the Internet – they are both packet switched networks and must be secured similarly.

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